Contraceptive effectiveness and safety are public health concerns of high national and international priority. The acceptability of a specific contraceptive method impacts significantly on the success of fertility control. Parenteral progestin contraceptives provide effective, long- term, reversible protection against pregnancy, but they often are discontinued because of abnormal bleeding patterns. The goal of this proposal is to understand the molecular and cellular mechanisms that underly irregular bleeding commonly associated with depot medroxyprogesterone acetate (DMPA) injections and levonorgestrel- containing silastic capsules (Norplant). Unlike the initiation of normal menses, which is triggered by spiral artery constriction, irregular bleeding associated with parenteral progestins is thought to originate from the subepithelial capillary plexus. Regulation of the endometrial microvasculature is understood poorly, but its growth and development are coordinated by ovarian hormones. We and others have demonstrated that a specific angiogenic peptide, vascular endothelial growth factor (VEGF), is hormonally regulated in human endometrium. We hypothesize that VEGF mediates the effects of ovarian steroids on the growth and function of the endometrial microvasculature. Progestational agents alter endometrial VEGF action, disrupting normal angiogenesis and regulation of endometrial microvessels. This disruption of endometrial vasculature, glands, and stroma ultimately leads to unpredictable, irregular uterine bleeding. Modern cellular and molecular approaches will be used to elucidate the biological bases for irregular bleeding associated with parenteral contraceptives. This information will allow the rational design of improved devices, or suggest adjuvants (e.g., estrogen) to ameliorate the irregular bleeding observed with parenteral progestin therapy, leading to improved acceptance of DMPA and Norplant. All integrated, multidisciplinary team of investigators with expertise in clinical contraception and basic laboratory investigation will address the following objectives: Specific Aims I: The ultrasonographic, hysteroscopic, microscopic and biochemical characteristics of the endometrium, including expression of VEGF and estrogen and progesterone receptors, will be examined in women using parenteral progestin contraceptives and in normal, ovulatory controls. Specific Aim II. The in vivo regulation of VEGF by ovarian steroids and the role of VEGF in endometrial angiogenesis will be studied in human endometrium transplanted subcutaneously in immunodeficient mice. Specific Aim III. The molecular regulation of endometrial VEGF by ovarian steroids and their receptors will be studied in isolated human endometrial epithelial and stromal cells in vitro. An understanding of the cellular expression of VEGF and the endocrine regulation of endometrial angiogenesis should provide new targets to improve the acceptability of these effective contraceptive devices.